sulin receptors in brain are structurally different from non-neural insulin ceptors. The alpha subunits of the brain insulin receptor migrate faster sodium dodecyl sulfate polyacrylamide gel electrophoresis, and this fference in molecular weight is thought to be due mainly to differences in ycosylation. To test whether this difference between brain and non-neural sulin receptor is specific to adult rats or whether it is more widespread, performed similar experiments in guinea pigs, chickens, lizards and ogs. In addition we examined fetal, neonatal and adult rats to determine en these differences begin ontogenetically. The findings demonstrate that ain insulin receptors are structurally different from liver insulin ceptors both ontogenetically and phylogenetically.